1. Field of the Invention
The invention relates to a system and related methods for irradiating substrates using a gas cluster ion beam (GCIB) and, more particularly, to systems having a cleaning apparatus to remove contamination from such systems.
2. Description of Related Art
Gas cluster ion beams (GCIB's) are used for doping, etching, cleaning, smoothing, and growing or depositing layers on a substrate. For purposes of this discussion, gas clusters are nano-sized aggregates of materials that are gaseous under conditions of standard temperature and pressure. Such gas clusters may consist of aggregates including a few to several thousand molecules, or more, that are loosely bound together. The gas clusters can be ionized by electron bombardment, which permits the gas clusters to be formed into directed beams of controllable energy. Such cluster ions each typically carry positive charges given by the product of the magnitude of the electronic charge and an integer greater than or equal to one that represents the charge state of the cluster ion. The larger sized cluster ions are often the most useful because of their ability to carry substantial energy per cluster ion, while yet having only modest energy per individual molecule. The ion clusters disintegrate on impact with the substrate. Each individual molecule in a particular disintegrated ion cluster carries only a small fraction of the total cluster energy. Consequently, the impact effects of large ion clusters are substantial, but are limited to a very shallow surface region. This makes gas cluster ions effective for a variety of surface modification processes, but without the tendency to produce deeper sub-surface damage that is characteristic of conventional ion beam processing.
Known GCIB systems of the type described above include a vacuum vessel within which the substrate is irradiated with the cluster ion beam. Over time, such irradiation has been observed to result in the accumulation of contaminants on the interior surfaces of the vacuum vessel. These contaminants may be the result of diverging cluster ion beams that do not reach the substrate, but instead reach interior surfaces of the vacuum vessel, or surfaces of the GCIB system components internal to the vacuum vessel. If those contaminants are left on these surfaces, they may eventually flake off, thereby contaminating the substrate doping, etching, cleaning, smoothing, layer-growing, or layer-depositing GCIB operation.
A need therefore exists for an apparatus and related methods to easily clean the interior surfaces of components of GCIB processing systems.